Process of manufacturing vinyl esters



Patented Aug; 9, 1927.

UNITE STATES? rnnnnnrcx w. sxrnnow AND o'r'ro w. nnn'zanne, or snawrmemFALLS, QUEBEC,

cameras, ABBIGNORS, BY MESNE assrcnman'rs, ro CANADIAN nnnc'rnornonuc'rs comm, nmrrnn, or monrnnnn, ennnnc, census.

FROCESS OF MANUFACTUBINQ VINYL EE'LERS.

Ho drawing.

This invention relates to improvements in the manufacture of vinylesters and the object of the invention is to provide a process by whichthe vinyl esters may be produced to such an extent that the process iscommercially and economically satisfactor I 1 is known that acetylene inthe presence of certain catalysts, such use mercury comound which isin asuitable physical con ition, will combine with carboxylic acids to yielddiesters of hypothetical ethylidene glycols. Thus, ethylidene diacetate1s formed by passing acetylene into glacial acetic acid in presence ofmercuric sulphate, the reaction taking place in accordance with Incarrying out this process, the production of ethylidene diacetate issomewhat under the theoretical amount, owing partly to the formation ofother bodies. It has been found that among the bodies thus indirectlyformed is a small amount of vinyl acetate.

It is possible that in the formation of diesters as above described,thevinyl esters are formed as an intermediate stage by the direct additionto acetylene to the carboxylic acids. In the case ofacetic acid, theaction would presumably be in accordance with the equation 0H,.COOH G HCH :CHDOGCH, If this is the case the vinyl ester presumably converts toa diester and a small amount remains in unsaturated condit on.

It has further been discovered that diesters.

on decomposition give as one of the prodnets of the reaction vinylesters with the liberation of one molecule of acid. Thus in the case of,ethylidene diacetate the re action takes place as follows 000.011 CH3'CHOOC.CH3

It may be pointed out that in the forma Application filed November 8,1920. Serial No. $2,698.

tion. of vinyl esters both by the action of acetylene oncarboxylic acidsand from diesters, the vinyl esters formed do not represent the greatestbulk of the products of the reaction but it has been discovered that theconditions of the reactions can be so regulated that suficient yields ofvinyl esters are obtained to make the process practical from amanufacturing standpoint.

In the manufacture of ethylidene diacetate bypassing acetylene throughacetic acid the acetylene gas passes through two condensers arranged inseries and is then returned to the reaction vessel, the first of thesecondensers being a water condenser maintained at about 70 to 100 C.to'condense acetic acid and the second being a brine condenser in whichaldehyde and other products are condensed. According to the process, thecondensate of both condensers is returned to the reaction.

Again, in the decomposition of ethylidene diacetate by means of sulphurdioxide in accordance with copending application Serial No. 422,665,filed November 8th, 1920,

such as sulphur dioxide, is increased to over 1% that the amount ofvinyl acetate formed is large, amounting to as high as 15% to 25% of thetheoretical amount.

The process according to this invention therefore consists in passinacetylene into a carboxylic acid at suite is temperature and pressure,the vaporous products of the reaction being passed through twocondensers arranged in series, the first of which is a reflux condenserarranged to return the acid and the diester to the reaction. and thesecond condenser being arranged to resolve the vaporous vinyl ester toliquid state. The diester which is formed by the reaction is thentreated, after purification if necessary, with a catalytic ordecomposing agent and heated, with the result that a further yield ofvinyl ester is obtained. It Wlll thus be seen that the process accordingto this invention comprises two stages, the first stage being a directroductlon of a vinyl ester by the combinatlon ot acetylene and acarboxylic acid and the second stage being the decomposition of aby-product of the first stage to yield further vinyl ester.

In carrying out the process, the temperature of reaction in the firststa e is maintained between 60 and 100 and the first condenser,preferably a Water condenser, between 70 and 100 C. The secondcondenser, preferably a brlne condenser, is maintained between C. and C.The reaction of the first stage is carried out by means of any suitablecatalyst, preferably mercuric sulphate obtained as a precipitate in theacid. The acetylene is used considerably in excess of the comblnableamount and external cooling is resorted to to control the temperature ofthe reaction. Uncombined acetylene may be returned to the reactionvessel for further use by means of a blower or other suitable apparatus.The yield of vinyl ester is 15% to of the theoretical amount.

In the second stage of the process, the diester is heated with asuitable catalyst to a temperature ranging between 100 C. and 170 C. ina reaction vessel fitted with a suitable reflux column to allow aldehydeand vinyl ester to escape but to condense and return to the reactionother decomposition products and undecomposed diesters. The temperatureat the top of thisv column is maintained during the reaction between 40and C. The aldehyde distilling over contains a. considerable amount ofvinyl ester while the reaction liquor itself contains much vinyl ester.After the reaction has proceeded until no more distillate comes over,which usually covers a period of 45 hours, the temperature at the top ofthe column is raised to approximately 110 C. by increased heating of theliquid to distill over vinyl ester which remains in the reaction liquor.'Using as a catalyst syrupy hosphoric acid, as explained in applicationerial No. 354,225, filed Jan. 26th, 1920, to an amount of approximately1.4% of the L whole, added slowly throughout the reaction,

the yield of vinyl ester will be about 15% of the theoretical amountobtainable, only about 80% of the diester having been acted upon. Theyield of vinyl ester may be considerably increased by using instead ofphoshoric acid an oxide of sulphur dissolved 1n the reaction liquor inamount up to 10% of the reaction li uor byweight. The yield will beincrease by approximately 10% of the theoretical amount, thus bringingthe yield up to 25% of the theoretical amount. The following exampleswill illustrate the invention Example 1- First stage.

10 lbs. of mercuric oxide is added to 100 lbs. of commercial acetic acidin a vessel provided with an agitator. After solution is completed withthe curic acetate and a smal amount of water, approximately 4 lbs. ofoleum is added,

roduction of merthe temperature being maintained between 70 and C-during the addition. The sulphuric anhydride in the oleum combines withthe previously liberated water to form sulphuric acid and the whole massof sulphuric acid precipitates the mercuric acetate as mercuricsulphate. Best results are obtained when approximately only that amountof sulphuric acid necessary to precipitate the sulphate is used. Thecatalytic agent, mercuric sulphate, is now found in a finely divided andvery reactive form. Acetylene is passed into the mixture greatly inexcess of the combinable amount, the

liquor being maintained preferably at a temperature between 80 and byexternal cooling and at the same time agitated. Acetylene is rapidlyabsorbed forming vinyl acetate and ethylidene diacetate. The unabsorbedacetylene gas carries out of the reaction vessel a considerable amountof acetic acid vapor and the major portion of the vinyl acetate whichhas not been converted to ethylidene diacetate. Some acetaldhyde vaporis also found. This gas and vapor mixture is a'ssed first through acondenser maintained at a temperature of 70 C. to C. The major portionof the acetic acid is condensed and goes back to the re action forreuse, a U-seal being preferably provided between the vessel andcondenser to avoid reverse flow. The remaining gas and vapor mixturepasses to a second condenser maintained preferably at a temperature of15 to +20 C. with the result that acetaldehyde and vinyl acetate arecondensed and may be collected. The unabsorbed acetylene may be returnedto the reaction by any suitable means. The vinyl acetate may be purifiedand separated by distillation from the acetaldehyde and the acetic acidcarried over.

Second stage.

The ethylidene diacetate found in the reaction vessel on the completionof.the first stage is preferably freed from sulphuric acid andundesirable bodies present in accordance with Patent No. 1,450,982,granted April 10th, 1923, in order to prevent decomposition and tarformation during purification if such is necessary. Sulphur dioxide gas,up to 10% of the diester by weight, is dissolved in the diacetate andthe int.

, 1920, may be employed and, in carrying out' this temperature, thetemperature at the top of the column is raisedto approximately 110 C.'byincreased applicatlon of heat to the liquid to distill over the vinylacetate, which remains in the reaction liquor. The yield obtained isfrom 15% to 25% of the theoretical amount, which with the yield of thefirst stage, amounting to 15% to 25% of the theoretical amount, gives atotal production to 25% to 45% ofthe theoretlcal, based on the amountsof acetylene and acetic acid originally used.

. Example 2. v The first stage of the process is conducted as in Example1 but in the second stage,

syrupy phosphoric acid to an amount of 0.4% is used as the catalytlcagent nstead of sulphur dioxide and 1s slowl added over a period ofapproximately elg t hours, the reaction being carried out undersubstantially the same conditions as described in the second stage ofExample 1. The yield of vinyl acetate obtained is approximately 15% ofthe theoretical amount obtainable.

In connection with the first stage of Example 1, it may be stated thatif thecondensate from the second condenser is returned to the reaction,as well as that from the first, the final yield of vinyl acetate will,

be very much lower, being approximately 3% and robably not over 5% atthe most.

If it is ound advisable, the first stage of the vinyl acetate thenobtained from the ethylidene diacetate. It may be mentioned thatwherever ethylidene diacetate is mentioned in the foregoing examplesthat it need not be absolutely ure but may be the commercial article, Wich contains anywhere from 5% to 20% of acetic acid. In carrying out theprocess accordin to the first stage of Example 1, any of t e alternativeconditions and catalytic agents, such as are given in detail incopending application Serial No. 422,885, filed November 8th,

the second stage, any of the alternative conditions described in coending application Serial No. 422,665, fi' ed November 8, 1920, may alsobe employed. While the examples deal with the aceticfester and diesterit will be understood that the steps of the process may be carried outwith any suitable modifications of the last mentioned applicationtoproduce esters and diesters of other carboxylic acids. For exoafample, vinyl formate and ethylidene diformate will be produced fromformic'acid and vinyl butyrate and ethylidene dibutyrate from but ricacid.

Although t e foregoing description specifically mentions only the use ofaceticacld and the formation of vinyl acetate,

it will be understood that the process applies generally to theformation of vinyl esters of all suitable aliphatic carboxylic' acidssuch as formic, propionic and butyric acids.

While the process is normally carried out at atmospheric pressure itWlll be understood that it may be carried out equally well atsub-atmospheric or super-atmos heric pressures. It will also beunderstoo that the temperatures mentioned will naturally be somewhatmodified according to the acids used and the esters formed, thepermissible temperatures, generally speaking, increasing as the hlghermembers of the series are dealt wlth. Y

Having thus described our invention, what we claim is 1 A process ofproducing a vinyl ester, which comprises bringing together an excess ofacetylene and a carboxylic acid in presence' of a cataclyst and removingthe vinyl ester as formed from the reaction by maintaining conditionssuch thatthe ester is carried out of the reaction in the escaping excessof acetylene.

2. A process of producing a vinyl ester which comprises bringingtogether in presence of a catalyst a carboxylic acid and acetyleneinexcess suificient to entrain va orous products of the reaction, andfractionally condensing the vaporous products to separate vinyl estersfrom diesters and acid and returning the diesters and acid to thereaction. 7

3. A process of making vinyl esters, which comprises causing-thereaction of acetylene 'as formed throughout.

and maintaining a tem erature between 100 and 170 C. an distil mg offthe vinyl ester 5. A process of making vinyl esters, which comprisescausing the reactiomof acetylene with a carboxylic acid in presence of amercury sulphate as catalyst, neutralizing mineral acid derived from thecatalyst, adding a fresh catalyst, increasing the temperature anddistilling oil the vinyl ester as formed during the whole operation.

4 6. A process according to claim 5, in which the reaction with thefirst catalyst is maintained at a temperature between 40 and 100 (3.,and the reaction with the second catalyst 'at a temperature between 100and 170 C.

7 A process of making vinyl acetate, which comprises reacting togetheracetylene and acetic acid in presence of mercury sulphate as catalyst,neutralizing mineral acid derived from the catalyst, adding a freshcatalyst and increasing the temperature and distilling ofi vinyl acetateas formed during the whole operation.

8. A process of making vinyl acetate, which comprises causing thereaction of acetylene and acetic acid in presence of mercury sulphate ascatalyst at a temperature between 40 and 100 0., adding fresh catalyticmaterial and increasing the temperature to between 100 and 170 0., anddistilling off and separating vinyl acetate as formed throughout theprocess.

9. A process of producing a vinyl ester, which comprises bringingtogether in presence of a mercury salt as catalyst a carboxylic acid andacetylene in excess sufficient to entrain vaporous products of reaction,while maintaining a temperature at which formed vinyl ester will distillolf, and removing the vinyl ester from the reaction in the escapingexcess of acetylene.

10. A process for the production of vinyl acetate, which comprisesreacting upon acetic acid with an excess of acetylene in presence of amercury salt as catalyst while maintaining a temperature at which theformed acetate will distill off, and removing the acetate from thereaction in the escaping excess of acetylene.

In witness whereof, we have hereunto set our hands.

FREDERICK \V. SKIRROW. OTTO W. HERZBERG.

